Degradation Of Crystal Violet And Malachite Green By Mg-Al Layered Double Hydroxides And Its Calcined Product As Fenton-like Reaction Catalysts

Mg-Al layered double hydroxide (Mg-Al LDHs) is a kind of nano-layered doublemetal hydroxides which can be used as adsorptive and catalytic material andundergoes the anionic exchange in solution. Calcined Mg-Al layered doublehydroxide (Mg-Al CLDHs) refers to the product of roasting magnesium aluminumhydroxide at a high temperature which destroyed its layered structure. But CLDHs bebetter than LDHs at adsorption properties. It can degrade dyes as the catalyst inFenton-like system effectively. This research is to study the catalytic oxidationperformance of Fenton-like system Mg-Al LDHs/H2O2and Mg-Al CLDHs/H2O2withcrystal violet and malachite green as reactants.This research includes several parts as follows:(1) To prepare Mg-Al LDHs atroom temperature by the solid-phase method;(2) To calcine Mg-Al LDHs to aquireMg-Al CLDHs;(3) To discuss the different factors such as initial pH, amounts ofconsumed catalyst and H2O2, initial concentration of dyes, reaction temperature andreaction time, etc. how to affect the degrading behaviors of crystal violet andmalachite green by Mg-Al LDHs/H2O2Fenton-like reaction;(4) To discuss thedifferent factors such as initial pH, amounts of consumed catalyst and H2O2, initialconcentration of dyes, reaction temperature and reaction time, etc. which effect thedegrading behaviors of crystal violet and malachite green by Mg-Al CLDHs/H2O2Fenton-like reaction;(5) To explore kinetics and mechanism of the Fenton-likedegradation process.The following conclusions were acquired:(1) The removal efficiency of crystal violet (40mg/L) could reach up to98%when Mg-Al LDHs dosage is0.01g, H2O2dosage is1.5mL, pH value is7, reactiontime is45min and reaction temperature is35℃. The removal efficiency of malachitegreen (60mg/L) could reach up to99%when Mg-Al LDHs dosage is0.01g, H2O2dosage is1mL, pH value is7, reaction time is30min and reaction temperature is30℃.(2) A same value of98%degradation of crystal violet can be obtained by adding0.005g catalyst of Mg-Al CLDHs and1mL oxidant of H2O2to a40mg/L dye wastewater with pH value of7at a constant temperature of35℃. The degradationvalue increase to99%when change concentration of malachite green dye wastewaterto30mg/L and add0.003g catalyst of Mg-Al CLDHs and1mL oxidant of H2O2to itat a pH value of7and a constant temperature with30℃for15min.(3) Kinetic study indicates that the degradation processes of crystal violet andmalachite green by Fenton-like system Mg-Al LDHs/H2O2and Mg-Al CLDHs/H2O2are coincidence to the kinetic first-order equation with a relatively well correlation.Both of correlation coefficients are lager than0.99.